1. Field of the Invention
The present invention relates to a microswitch.
2. Prior Art Statement
A typical microswitch is shown in FIG. 1 as one of conventional general microswitches. A switch casing 102 is constructed by a cover 101 and a switch casing main body 103. A pair of a terminal member for normally closed contact and a terminal member 105 for normally open contact and a common terminal member 106 are fixed to the main body 103. Fixed contacts 107 and 108 are fixed to inner end portions 104a and 105a of the fixed terminal members 104 and 105, respectively. A movable contact member 110 is pivotally supported to the inner end portion 106a of the common terminal member 106 at the base end thereof. The movable contact member 110 has a movable contact 109 at the front end thereof, the movable contact 109 being come into contact with or removed from the fixed contacts 107 and 108, respectively. A compression leaf spring 111 is attached between the front end side of the movable contact member 110 and the inner end portion 106a of the common terminal member 106. A push button 112 is inserted into a hole 102a formed in the top plate of the switch casing 102. By depressing the push button 112, the movable contact member 110 is moved, thereby switching the contacting state of the movable contact 109 from the normally closed type fixed contact 107 to the normally open type fixed contact 108 by the snap action.
However, in such a microswitch, since the movable contact member 110 is directly operated by the push button 112, a degree of whole motion (a travelling amount of the push button 112 from its free position to the operating limit position) is small and its operating stroke amount is also limited to up to about 1 mm.
To solve this problem, means for assuring a large operating stroke is shown in FIG. 2. That is, the push button 112 is operated by an operating lever 113 which is pivotally attached to the switch casing 102. FIG. 3 shows another means for realizing a large operating stroke, in which a sub-button 115 which is pressed downwardly through a spring member 114 is inserted in the push button 112 and the movable contact member 110 is operated by the sub-button 115. However, the former means has a drawback such that a large space is needed for the operating lever 113. The latter means has a drawback such that the number of parts increases.
On the other hand, in any of the foregoing conventional microswitches, their operating characteristics are as shown in FIG. 4 and a load near the operating limit position suddenly increases, so that the good operating feeling cannot be obtained.